SSB demod, was Re: carrirer oscillator
- --- In firstname.lastname@example.org, Robert McGwier <rwmcgwier@c...>
> This is not what we do on the Softrock40. The 11 kHz IF is used inthe
> SDR-1000 in order to do exactly what Frank says and that is avoid1/F,
> DC, junk, noise, etc. at 0. We are attempting to maximize theperformance.
Could you resume in a few sentences the difference between the
SoftRock-40 and the SDR-1000 in this regard?
I could go back to the articles on the SDR-1000 and try to figure it
out, but I think that you can give a better answer.
The softRock-40 has a fixed oscillator and can software-tune +/- 24
kHz around that frequency which means that near the oscillator
frequency we get "junk". With the SDR-1000 what happens when we tune
a particular frequency?
Jean-Claude Abauzit, PJ2BVU
- When tuning an SDR 1000, if spur reduction is turned off, the DDS is tuner
11025 khz below the frequency of interest and the software (DttSP)
oscillator is set to -11025 khz to recover the frequency of interest. This
works well but for the spurs from the DDS.
If spur reduction is turned on (the normal case) the DDS is tuned to the
nearest low spur point (as documented by some of the AD docs) and then
DttSP oscillator is set to an appropriate value to recover the signal of
interest. This generally results in a DttSP oscillator value between -9.5
and -12.5 khz.
On the SoftRock all the tuning is done with the DttSP oscillator and it
ranges over +/- 24 khz - giving a tuning range of 48 khz.